COMACO Gliricidia/maize intercropping field. Photo credit: Christian Thierfelder/CIMMYT.
Addressing smallholder farmers’ needs with green manure cover crops and agroforestry in Zambia
In Africa, mineral fertilizer remains a scarce, expensive, and risky resource for most smallholder farmers. On average, farmers use less than 10 kg/ha of NPK fertilizer; and many do not apply it at all. The price of fertilizer is 3-5 times higher in Africa than in Europe due to the lack of infrastructure and production facilities, often making it unaffordable and sometimes inaccessible to farmers. Fertilizer is primarily applied to higher value and horticulture crops that, unlike maize, give farmers a greater return on their investment.
Farmers in southern Africa plant maize extensively on large areas, harvest less than 2 t/ha on average, extracting already depleted nutrients from the soil while trying to become food secure and escape from poverty―an impossible task!
In Eastern Province of Zambia, farmers are being offered a range of solutions by Africa RISING that provide a way out of this poverty trap. These technologies, options, and approaches include drought- and stress-tolerant maize germplasm, conservation agriculture (CA), improved rotation and intercropping with grain legumes, agroforestry, and green manure cover crops.
The use of CA principles (minimum soil disturbance, crop residue retention, and diversification through rotation and intercropping) hinges on the ability of farmers to retain sufficient surface crop residues to protect the soil from erosion, runoff, evaporation, and excessive temperatures. However, farmers in mixed crop-livestock systems face competing demands for these residues because they also feed them to their animals. Green manure and selected agroforestry species are therefore grown to improve the soil, generate biomass for ground cover, and provide fodder; some also produce high protein grain for food, feed, or for sale on the market.
For the past six cropping seasons, CIMMYT and its partners have tested a range of species. Crops such as velvet bean, lablab, cowpea, sunnhemp, jack bean, pigeonpea, and Gliricidia, have been identified as viable options with great potential for smallholders. In some cases, they can provide 5-50 t/ha of extra biomass for groundcover and/or fodder, leave up to 350 kg/ha of residual nitrogen in the soil and in most cases, do not need extra fertilizer to grow.
Read the full story: Africa Rising
Author: Willem Van Cotthem
Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development. View all posts by Willem Van Cotthem